GB1575653A - Reinforced composites - Google Patents

Description

PATENT SPECIFICATION ( 11) 1575653

M ( 21) Application No 23174/77 ( 22) Filed 1 June 1977 g ( 23) Complete Specification filed 10 May 1978 ( 19) ( 44) Complete Specification published 24 Sept 1980 ( 51) INT CL C 081, 79/08//B 32 B 27/04, 27/34 C ( 52) Index at acceptance C 3 R 22 C 22 D 1 AX 22 D 2 B 1 22 D 2 BX 22 N 3 22 Pl 22 PX 22 T 2 C 5 B 1 C 6 X C 8 P L 1 B L 2 CX L 2 X L 6 A B 5 N 2704 2734 C 3 V BE C 3 W 210 225 309 C 3 Y B 262 B 284 B 285 B 286 G 315 G 320 ( 72) Inventor GEORGE EDWARD GREEN ( 54) REINFORCED COMPOSITES ( 71) We, C 1 BA-GEIGY AG, a Swiss Body Corporate of Basle, Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to reinforced composites containing photopolymerised and 5 thermosettable compositions and fibrous reinforcing materials, and to methods for their production.

Composite structures are commonly made by impregnating fibrous materials, such as fibres of paper, glass, aromatic polyamide, or carbon, metal filaments, and whiskers, usually in the form of layers, with a solution, in a volatile solvent, of a 10 solid thermosettable resin and a heat-activated curing agent for the resin, causing the resin to solidify by evaporation of the solvent, and, when desired, curing the resin composition in the resultant so-called "prepreg" by the action of heat Frequently, the prepregs are stacked before heat-curing, so that a multilayer laminate is formed.

Sheet moulding compounds are made by impregnating chopped fibrous rein 15 forcement with a liquid thermosettable resin, and then causing the resin to thicken by chemical means such as by reaction of carboxyl groups in the resin with magnesium oxide The resin is subsequently heat-cured.

Composite structures may also be prepared from films of a thermosettable resin composition by laying a film of the composition containing the resin and curing agent 20 on a fibrous reinforcement and applying heat and pressure so that the resin composition flows about the fibres but remains curable, and then heating further when desired so that the resin composition is cured by the heat-activated curing agent.

These methods suffer from certain drawbacks Some thermosettable resin compositions are solid, and if a solvent is used to dissolve the components of the com 25 position it is not always possible to eliminate all traces of it before the final curing takes place, and in consequence the cured composite may contain voids caused by evaporation of such residual solvent Solvents may cause difficulties due to their toxicity or inflammability or to pollution If a film adhesive is used, it is usually cast from a liquid thermosettable resin and this is then advanced to the solid state; 30 such a process adds considerably to the cost of the composite The methods also require a considerable expenditure of heat energy, either to evaporate the solvent or to advance the resin.

In recent years, thermosetting resins containing maleimide or similar groups have become of interest; however, they sometimes present difficulties in the production of 35 composite structures from them, since they, and preferred curing agents therefor, are often solids and cannot readily be thickened for the production of sheet moulding compounds These thermosetting resins have to be applied to the fibrous reinforcement from solution in an organic solvent, such as N,N-dimethylformamide or dimethyl sulphoxide, with the disadvantages just mentioned Further, they have not hitherto 40 been readily obtainable in film form.

We have now found that fibre-reinforced composites, containing a thermosettable resin composition as the matrix material, may be obtained by impregnating the fibrous reinforcement with such a resin and a photopolymerisable compound and photopolymerising the latter, or by preparing a film from the resin and the photopolymerisable compound and impregnating the reinforcement with the film, without the need to incur the disadvantages set out above.

Accordingly, this invention provides thermosettable composites comprising (a) a fibrous reinforcing material, (b) a heat-curable polyamide resin containing, per average molecule, at least two groups of formula /CO CO directly attached to carbon atoms, where D denotes CH,-C CH,=C or, preferably, H 10 H CH CH CHC (hereinafter, referred to as a "polvimide resin"), (c) a heat-activated curing agent for the polyimide resin, and (d) a photopolymerised compound.

British Patent Specification No 1377 816 discloses photocrosslinkable compositions containing (i) a film-forming resin having one or more allyl ester groups and 15 (ii) a compound containing one or more maleimido groups The photocrosslinked films which are produced may be further crosslinked by heating to 500 However, the compositions do not contain a heat-activated curing agent for the compounds containing maleimido groups, and the maleimido compound is stated to act both as a copolymerisable component and as a photoinitiator 20 It is not necessary, in the present invention, to convert immediately the polyimide resin in the photopolymerised composition distributed on the fibres into the fully cured, insoluble, and infusible C-stage; often, it can be changed into the still fusible B-stage, or remain in the A-stage, and, when desired, e g, after stacking, and/or after the composite has been formed into some desired configuration, fully cured by 25 heating For example, if a hollow shaped article is required, it is convenient to impregnate a continuous tow of fibrous reinforcement and wind the tow around a former while, at the same time, exposing the winding to actinic radiation Such windings still have a certain degree of flexibility, permitting the former to be removed more easily than when a rigid winding is formed in one step When required, the 30 filament winding is heated to complete the cure.

Also included in this invention are a method of making a reinforced composite which comprises heat-curing a photopolvmerised, but still thermosettable, composite of this invention, and heat-cured, reinforced composites made thereby.

A convenient method of preparing the composites of this invention comprises 35 i) impregnating a fibrous reinforcing material (a) with a liquid composition comprising (b) a heat-curable polyimide resin (as herein defined), (c) a heat-activated curing agent for a polvimide resin, (d) a photopolymerisable compound (other than a polyimide resin) and, if 40 desired, (e) a photonolvmerisation catalyst for the compound d), and ii) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of the polyimide resin, exposing the impregnated material to actinic radiation such that, the composition solidifies due to photopolymerisation of 45 the said photopolymerisable compound while the polyimide resin remains substantially in the thermosettable state.

This method is particularly useful for the production of filament windings, and, when chopped strand reinforcing material is used, for the production of sheet moulding compounds 50 1,575,653 3 1,575,653 3 Another method of preparing composites of this invention from fibrous reinforcing material (a) comprises i) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of polyimide resins (as herein defined), exposing to actinic radiation a layer of a liquid composition comprising 5 (b) a heat-curable polyimide resin, (c) a heat-activated curing agent for a polyimide resin, (d) a photopolymerisable compound (other than a polyimide resin), and, if desired, (e) a photopolymerisation catalyst for the compound (d), until the said com 10 position solidifies to form an essentially solid continuous film due to photopolymerisation of the said photopolymerisable compound while the polyimide resin remains substantially in the thermosettable state, and ii) bringing together the film so formed and the fibrous reinforcing material (a) under conditions such that the said film flows about the fibres and the com 15 ponents of the said film and the fibres form a coherent structure but the polyimide resin remains substantially thermosettable.

The latter procedure is particularly convenient when unidirectional fibrous reinforcement is to be used in the production of prepregs, especially if the fibres are short and/or light, because there is less tendency for the fibres to become displaced and 20 the reinforcing effect thereby becomes irregularly distributed.

Usually the film and fibrous reinforcing material are brought together with the application of heat and/or pressure The period of heating can be very short (thereby avoiding curing of the polyimide resin), as there need be no solvent to evaporate and the film need not be thick 25 Compositions used to prepare the thermosettable composites of the present invention must be liquid under the conditions used in making the films or in impregnating the reinforcing material before irradiation but are preferably solvent-free.

The reinforcement may be in the form of woven or non-woven cloth, unidirectional lengths, or chopped strands and may be of natural or synthetic fibres including 30 strands and filaments, especially glass, boron, stainless steel, tungsten, alumina, silicon carbide, asbestos, potassium titanate whiskers, an aromatic polvamide such as polv(mphenvlene isophthalamide) or polv(p-phenvlene terephthalamide), or carbon.

The preferred polyimide resins are of the formula D\ w N-R 1-N\ D II 35 CO C Oa where D has the meaning previously assigned, RI is an organic group of valency (a+ 1), containing from 2 to 30 carbon atoms, and a is 1 or 2 40 Further preferred polvimide resins are those of formula II wherein R' denotesa linear or branched alkvlene radical of 2 to 12 carbon atoms; a phenylene radical, optionally substituted in the ring by 1 to 3 methyl groups or by 1 to 3 fluorine, chlorine, or bromine atoms; a cyclohexylene radical, optionally substituted in the ring by I to 3 methyl groups; 45 a radical of formula (CH 2)b (CH 2)bin which b is an integer of from I to 3; a radical of formula 1,575,653 R 2 R 3 CC-0 .I I -C 3 H 6-N /N C 3 H 6IV C I a radical of formula R 54 j.% 5 5 LG 3 H 61-N R 2 R 3 \ / C C C=O I N C 3 H 6 Ii ? where R 2,, R, R', and Rs each denote a hydrogen atom or the same or a differentaliphatic hydrocarbon group of 1 to 6 carbon atoms, with the proviso that R 2 and R' may alternatively, together with the carbon atom to which they are attached, form a or 6-membered aliphatic ring; a phosphate-, thiophosphate-, phosphite or thiophosphite-containing radical of formula -R 6LR 70 H f R 8 j VI where a has the meaning previously assigned, R 6 denotes an aromatic residue of valency a+ 2, containing 6 to 15 carbon atoms, especially a mononuclear benzenoid group or a dinuclear benzenoid group the nuclei of which may be fused, or joined by a carbon-carbon bond only, or joined through an oxygen atom, an alkylene group, or a sulphonyl group, R 7 denotes a monovalent aromatic group of 6 to 15 carbon atoms, especially a mononuclear benzenoid group, R 8 denotes an oxygen or sulphur atom, and c denotes zero or 1; a radical of formula V 1,575,653 VII a radical of formula R 9VIII where R 9 denotes a methyl group or a chlorine atom, d denotes zero or an integer of 1 to 4, and R 10 denotes a carbon-carbon bond, or an atom or group of formula -0-, -S-, -CGO-, -CH 2-, -C(CH 3),2-, -SO 2-, -CONH-, -COO-, -CONHR'-CONH-, -N:N-, or -NR'-, wherein R' and R 4 have the meanings previous assigned; and especially a radical of formula R 9 R 10 Rd d P 9 IX where R 9, d, and R' have the meanings previously assigned.

Examples of specific polyimide resins are bis( 4 maleimidophenyl)methane, bis( 4 itaconamidophenyl)methane, bis( 4 citraconamidophenyl)methane, 2,2 bis( 4 maleimidophenyl)propane, bis( 4 maleimidophenyl) sulphone, bis( 4 maleimidophenyl) ether, bis( 4 maleimidophenyl) ketone, 1,6 bis(maleimido) hexane, the isomers of formula CO,NCO 77 N X and 1,3 and 1,4-di(maleimido)benzene.

Such polyimide resins are, in general, known, and can be manufactured by the methods described in United States Patent Specification No 3 018 290 and British

Specification No 1 137 592, involving reaction of the appropriate polyamine with the unsaturated dicarboxylic acid anhydride in a polar solvent and in the presence of a catalyst.

Heat-curing agents, ie, those which induce addition polymerisation of the poly 5 imide resin on heating, are well known They are usually dissolved or suspended in the liquid composition before impregnation of the reinforcement, and an amount effective for curing is employed.

Examples of the preferred agents include diamines and triamines of formula H 2 N-Ri+NH 2 l 10 XI where RI and a have the meanings previously assigned, particularly those where R' denotes a divalent radical of formula IX Specific examples are bis( 4 aminophenyl)methane, bis( 4 aminophenyl) phenyl phosphate, m phenylenediamine, hexamethylenediamine, 1,3 bis( 3 aminopropyl) 5,5 dimethylhydantoin, and 2,2bis( 4 aminophenyl)propane The use of such amines to cure polyimide resins is S 15 described in, e g, British Patent Specification No 1 190 718.

Other curing agents are polyhydric phenols, including mononuclear phenols such as hydroquinone, phloroglucinol, pyrocatechol, and resorcinol, and dinuclear phenols such as those of formula R 11 R 11 HO OH XII 20 R / where R is chlorine or bromine, R 2 denotes -CH 2-, -C(CH))2-, -SO 2-, or -S-, and c and d have the meaning previously assigned, and those containing condensed rings, such as 1,4-dihydroxynaphthalene, and also novolaks of formaldehyde and 25 phenol, cresol, p-chlorophenol, p-tert butylphenol, p-octylphenol, or pnonylphenol.

The use of such curing agents is described in German Auslegeschrift No.

2 459 925.

Other suitable curing agents are alkenvlphenols or ethers thereof, such as those with saturated or ethylenically unsaturated aliphatic alcohols of up to 6 carbon atoms, 30 preferablv an allyl or methallyl-substituted phenol or an ether thereof, including mononuclear compounds such as eugenol and its methyl ether, or a bi or trinuclear compound containing at least one allyl group and an optionally ethereified phenolic hydroxyl group attached to at least one nucleus thereof, especially a compound of formula 35 CH 2 CH=CH 2 HO 4 R 12 OH xn II CH 2 =CHCH 2 XII where RI' and c have the meanings previously assigned.

The use of such phenols and phenol ethers is described in German Auslegeschrift No 2 627 045.

1,575,653 7 L 5 i 5 7 Other suitable curing agents include polyhydric alcohols Preferably, di or trihydric alcohols are employed, such as branched or straight chain aliphatic alcohols of 2 to 12 carbon atoms, e g, ethylene glycol, 1,1,1-tris(hydroxymethyl) propane, and glycerol, and also cycloaliphatic and cycloaliphatic-aliphatic alcohols of up to 12 carbon atoms with one or more cycloaliphatic nuclei, which may be joined by an oxygen or sulphur atom, a carbon-carbon bond, or an aliphatic group, wherein the hydroxyl groups are attached to either aliphatic or cycloaliphatic residues, especially those of formula XIV or R 13 HOCHCH 2 HOCHCH 24 R 13 I CHOH XV and araliphatic alcohols of the formula R 13 I HOCHCH 21 R 13 I OCH 2 CHOH XVI where R 12 and c have the meanings previously assigned and each R'3 denotes a hydrogen atom or a methyl group.

Use of such polyhydric alcohols as curing agents for polyimide resins is described in German Auslegeschrift No 2 459 961.

A further class of curing agents includes polycarboxylic acids, as described in German Auslegeschrift No 2 459 938 Di and tricarboxylic acids are preferred, especially an aliphatic dicarboxylic acid of 4 to 10 carbon atoms, such as succinic, glutaric, adipic, 2,2,4 and 2,4,4-trimethyladipic, pimelic, and sebacic acid.

Other curing agents include azomethines of formula Ri 5 I R'4 _C = N T Rle XVII or R's R 15 i NRN R 11-d = N-R 1-N = G-W' XVIII 1,575,653 8 1,575,653 8 or R'4 R 14 R 4-N= C-R 7-C=N R 16 XIX in which R 4 denotes a hydrogen atom, a linear or branched aliphatic radical of up to 12 carbon atoms, a cycloaliphatic or cycloaliphatic-aliphatic radical of up to 12 carbon 5 atoms, an aromatic radical of 6 to 12 carbon atoms, an araliphatic radical of 7 to 20 carbon atoms, a heterocyclic radical of 4 to 7 carbon atoms, or a heterocyclic-aliphatic radical of 5 to 18 carbon atoms, RI and R 16 have the same meaning as R 4 except that they cannot denote a hydrogen atom, with the proviso that R 4 and R 15 in formulae XVII and XVIII, 10 together with the carbon atom to which they are attached, can also denote a 5 or 6membered aliphatic ring, R 1 denotes a divalent linear or branched aliphatic radical with up to 12 carbon atoms, a divalent cycloaliphatic or cycloaliphatic-aliphatic radical with up to 12 carbon atoms, a divalent aromatic radical of 6 to 12 carbon atoms, a divalent arali 15 phatic radical of 7 to 18 carbon atoms, a divalent heterocyclic radical of 4 to 7 carbon atoms, or a divalent heterocyclic-aliphatic radical, and R' is a divalent radical having the meaning previously assigned.

Use of such azomethines is described in British Specification No 1 443 067 and

United States Patent Specification No 3 944 525 They may, as described in British 20

Specification No 1 446 177, be used in conjunction with polyamines such as those of formula XI.

Other suitable curing agents are dimeric, or oligomeric, halogencontaining bis(cyclopentadienyl) compounds of formula (H)4-e R 13 R 13 25 -CH CH 25 2 2 X (R 18/e where R 8 denotes a fluorine, chlorine, or bromine atom, e is an integer of 1 to 4, each R 3 has the meaning previously assigned, and f is an integer of average value 2 to 20 30 The use of such curing agents for polyimide resins is described in British Specification No 1 424 075.

There may also be employed as curing agents fl-aminocrotonic acid and its derivatives, as described in German Auslegeschrift 2 529 092, and also indole and its derivatives, as described in German Auslegeschrift 2 544 900 35 The former are suitably of any of the following formulae NHR 19 CH 3 CZ=CHC R 20 X CH 3 C CHCOO R _ -9 NHR 19 CH 3 C CHCONR 19 R 20 3 -g XXII NHR 19 R 21 NHR 19 1 I 11,I CH 3 C=CHCON 1,NCOCH-CCH 3 R 21 X Xi CH 3 R 19 OCOCH CNH R 20 xxiv g R 22 CH 3 I I R 19 NCOCH=C-NR 19-R 20 xxv XXV NHR 19 I XXVI and CH 3 C=CHCOR 23 R 24 XXVI NHR 19 R 19 NHR 19 I 20 i I CH 3 C=CHCOOR 20 NCOCH CCH 3 xxv II where R'9 and R" each denote a hydrogen atom or a linear, branched, or cyclic hydrocarbon radical of 1 to 9 carbon atoms, R 20 denotes a divalent linear, branched, or cyclic hydrocarbon radical with 2 to 10 carbon atoms, or a heterocyclic ring containing one or more nitrogen, oxygen, or sulphur atoms, R 21 and R 21, are such as to form with the two indicated nitrogen atoms a heterocyclic five or six-membered ring, R 2 ' denotes -0or -NH-, 15 R 24 denotes a linear, branched, carbocyclic or heterocyclic radical with 3 to 6 carbon atoms, having a group suitable for polymerisation, such as an allyl group or a group of formula 1,575,653 1,575,653 c H XXVIII and g is an integer of 2 to 4.

Suitable indoles are of formula N 2 6 R 26 X R 25 where 5 R 2 denotes a hydrogen atom, an alkyl group of 1 to 4 carbon atoms, or an acyl group of 2 to 5 carbon atoms, and R 16 denotes a hydrogen atom or an alkyl group of 1 to 4 carbon atoms.

Acetone-anil, i e, 2,2,4-trimethyl-1,2-dihydroquinoline, may also be used as the curing agent (see German Offenlegungsschrift 2 715 217) 10 If desired, a mixture of curing agents, e g, of polyamines with polyhydric phenols or polyhydric alcohols, may be used.

It is within the scope of the invention to employ the polyimide resin and its heatcuring agent in the form of a prepolymer, especially when the agent is a poly-primary amine 15 Where members of the above classes of curing agent are of insufficient reactivity, this can often be rectified by adding an ionic, particularly a basic, catalyst, such as a quaternary ammonium base or a sodium alkoxide, but especially a secondary or tertiary amine, such as diethylamine, triethylamine, imidazole, quinoline, benzylamine, N-methylpyrrolidone, or bis(p-dimethylaminophenyl)methane Typical amounts are 20 from 0 01 to 5 %, and particularly 0 25 to 0 5 %, calculated on the total weight of the curable mixture.

A free-radical curing catalyst may also be added, e g, an organic peroxide or a persalt Compounds such as di-tert butyl peroxide, dilauryl peroxide, dicum yl peroxide, tert butyl cumyl peroxide, or tert -butyl perbenzoate, used in similar concen 25 trations to those in which ionic catalysts are employed, are examples of suitable compounds for this purpose.

The photopolvmerisable compound used in processes of the present invention may be of any chemical type known to polymerise under the influence of actinic radiation.

Such materials are described in, for examile, Kosar, " Light-sensitive Svstems: 30 Chemistry and Applications of Non-Silver Halide Photographic Processes", Wiley, New York, 1965.

As is well known, these materials fall into two main classes (i) those which are polymerised through a free-radical chain reaction (photoinitiated polymerisation) and 35 (ii) those in which polvmerisation is effected by reaction of an excited molecule of the monomer with an unexcited molecule of the monomer.

The first type require only one photopolymerisable group per molecule to form long chains on polymerisation while the second type must have at least two photopolvmerisable groups per molecule, since if they have only one such group per 40 molecule thev will dimerise, but not polymerise, on irridiation.

Photopolvmerisable substances of the first type preferred for use in this invention have one ethvlenic linkage, or more than one providing they are unconjugated Preferred examples of these substances are acrvlic esters containing at least one group of the general formula XXX, XXXI, or XXX II 45 00 XXX CIHL=C(R 2)COO XXX l CH = C(R 2) CONH-l_ CHCOO XX XXXII CH =C(R'7)CONHCH(OH)CH O COO XXXI & -lX 6 1 where R 27 is a hydrogen, chlorine, or bromine atom, or an alkvl hydrocarbon group of 1 to 4 carbon atoms, especially a hydrogen atom or a methyl group Groups of any of formulae XXX to XXXII may be attached directly to carbon atoms of, e g, radicals of from 5 to 50 carbon atoms More specific examples of acrvlates are 22dimethvlpropane-1,3-diol diacrylate and the esters of formulae XXXIII, XXXIV, 5 and XXXVI to XXXVIII below Other examples of substances of this type are styrene and crotonic acid.

Formula XXXIII is CH 2-=CHCOO (CH 2)h-(CHR 28)c-CHO-OCCH CH 2 R 29 where 10 c has the meaning previously assigned, h is an integer of 1 to 8, j is an integer of 1 to 20, R 8 denotes -H -OH or -OOCGH=CH,, and R 29 denotes -H, -CH?, -CH, H CHOH, or -CHROOCCH=C Hq 15 Examples of compounds of formula XXXIII are triethylene glycol diacrylate and tetraethylene glycol diacrvlate.

Formula XXIV is R 30 1 R 1 CH 2-CHCOO-(CHR 2)k 1 _R 28 _c j -e c, e, j, and R 2 have the meanings assigned above, 20 k is zero or a positive integer, preferably of not more than 8, provided that c and k are not both zero, R 3 denotes -H, -Cl, -CH 3, or -C 2 Hs, and R 3 denotes an organic radical of valency e, linked through a carbon atom or carbon atoms thereof to the indicated e terminal oxygen atoms, preferably the hydro 25 carbon residue of an aliphatic alcohol containing from 1 to 6 carbon atoms, such as -CH 3 or -CH 2 CH 2c / XXXV /%\ -CH CH 2A specific example is 2-methoxvethyl acrylate.

Formula XXXVI is 30 OH 1.575,653 12 1,575,653 12 where c and e have the meanings previously assigned and R 32 denotes an organic radical of valency e, linked through a carbon atom thereof other than the carbon atom of a carbonyl group.

More particularly, when c is zero, R 32 may denote the residue, containing from 5 1 to 18 carbon atoms, of an alcohol or phenol having e hydroxyl groups.

R 32 may thus represent, for examplean aromatic group (which may be substituted in the ring by alkyl groups), an araliphatic, cycloaliphatic, heterocyclic, or heterocycloaliphatic group, such as an aromatic group containing only one benzene ring, optionally substituted by chlorine 10 or by alkyl groups each of from 1 to 9 carbon atoms, or an aromatic group comprising a chain of two benzene rings, optionally interrupted by ether oxygen atoms, aliphatic hydrocarbon groups of 1 to 4 carbon atoms, or sulphone groups, each benzene ring being optionally substituted by chlorine or by alkyl groups each of from 1 to 6 carbon atoms, 15 or, preferably, a saturated or unsaturated, straight or branched-chain aliphatic group, which may contain ether oxygen linkages and which may be substituted by hydroxyl groups, especially a saturated or monoethylenically-unsaturated straight chain aliphatic hydrocarbon group of from I to 8 carbon atoms.

Specific examples of such groups are the aromatic groups of the formulae CH 20 and -CGHCH,, in which case e is 1, -CHC(CH)2 GC 6 H,-, and -C 6 HCH 2 CH -, in which case e is 2, and -C 6 H 4 (CH 2 CH 3-)a-CH 2 C 6 H,-, where a has the meaning assigned above, in which case e is 3 or 4, and the aliphatic groups of formula -CH 2 CHCH 2 or -CH 2 CH(CH 2)3 CH 2-, in which case e is 3, or -(CH 2)4-, -CH 2 CH=CHCH 2-, -CH 2 CH 2 OCH 2 CH 2-, or 25 -(CH 2 OCH 20)2 CH 2 CH 2-, in which case e is 2 or -(CH 2)3,C Hg, -(CH 2) OH, -CH 2 CH = CH 2, -(CH 2) 20 H, -CH CH(CH 3) OH, or-CH 2 CH = CHCH 20 H, in which case e is 1.

When c is 1, R 32 may represent the residue, containing from 1 to 60 carbon atoms, of an acid having e carboxyl groups, preferably a saturated or ethylenically-unsaturated, straight chain or branched aliphatic hydrocarbon group of from 1 to 20 carbon atoms, which may be substituted by chlorine atoms and which may be interrupted by ether oxygen atoms and/or by carbonyloxy groups, or a saturated or ethylenically-unsaturated cycloaliphatic or aliphaticcycloaliphatic hydrocarbon group of at least 4 carbon atoms, which may be substituted by chlorine 35 atoms, or an aromatic hydrocarbon groups of from 6 to 12 carbon atoms, which may be substituted by chlorine atoms.

Further preferred are such compounds in which R 32 represents a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of 40 from 1 to 8 carbon atoms, optionally substituted by a hydroxyl group, or a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of from 4 to 50 carbon atoms and interrupted in the chain by carbonyloxy groups, or a saturated or ethylenically-unsaturated monocyclic or dicyclic cycloaliphati 45 hydrocarbon group of 6 to 8 carbon atoms, or an ethylenically-unsaturated cycloaliphatic hydrocarbon group of from 10 to 51 carbon atoms, or a mononuclear aromatic hydrocarbon group of from 6 to 8 carbon atoms.

Specific examples of these residues of carboxylic acids are those of the formul 50 -CH,, -CH 2 CH 8, -CH 2 CH(OH)CH 3, -CH 2 CI, and -CGH, in which case e 1, and -CH 2 CH 2-, -CH-=CH-, and -C 6 H 4-, in which case e is 2.

Specific examples of suitable compounds of formula XXXVI are 1,4 bis( 2hydroxy 3 (acryloxy)propoxy)butane, a poly( 2 hydroxy 3 (acryloxy)propyl) ether of a phenol-formaldehyde novolak, 1 ( 2 hydroxy 3 (acryloxy) 55 propoxy) butane, -n octane, and N decane, bis( 2 hydroxy 3 (acryloxy)propyl) adipate, 2 hydroxy 3 (acrvloxy)propyl propionate, and 3 phenoxy 2hydroxypropyl acrylate.

Formula XXXVII is Rj C-CHOOCCH = CH 2 60 where R denotes CH:-, C 2 H 5-, or GCH 2-= CHCOOCH 2-.

13 1,575,653 Examples of such acrylates are pentaerythritol tetra-acrylate and 1,1,trimethylolpropane triacrylate.

Formula XXXVIII is CI 2 = CHCOOR'" where R'4 denotes either an alkyl group of 1 to 6 carbon atoms, optionally 5 substituted by one hydroxyl group, such as an ethyl, n-propyl, n-butyl, 2hydroxyethyl, or 2-hydroxypropyl group or a dialkylaminoalkyl group containing in all 3 to 12 carbon atoms, such as a diethylaminoethyl group.

Photopolymerisable materials of the second type include those having at leasttwo, and preferably three or more, groups which are azido, coumarin, stilbene, di 10 substituted maleimide, pyridinone, chalcone, propenone, or pentadienone groups, or acrylic acid groups which are substituted in their 3-position by groups having ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond of the acrylic group.

Examples of suitable azides are those containing at least two groups of the formula 15 Na-R 3 _ 5 XXXIX or N 3-SO-R 33 XL where R denotes a mononuclear or dinuclear aromatic radical containing from 6 to 12 carbon atoms, especially a phenylene or naphthylene group 20 Examples of suitable coumarins are those containing groups of the formula O= c R 36 XLI where RW 6 is an oxygen atom, a carbonyloxy group (-COO-), a sulphonyl group, or a sulphonyloxy group.

Examples of photopolymerisable materials containing stilbene groups are those 25 having groups of the formula C 7 H-UCH 3 -XLII R 37 where R: is the residue, containing up to 8 carboll atoms in all, of a five or sixmembered nitrogen-containing heterocyclic ring, fused to a benzene or naphthalene nucleus, and linked through a carbon atom of the said heterocyclic ring adjacent to a 30 nitrogen heteroatom thereof to the indicated benzene nucleus, such as benzimidazolyl, benzoxazolyl, benzotriazolyl benzothiazolyl, or a naphthotriazolyl residue.

Examples of photopolymerisable materials containing disubstituted maleimide units are those having groups of the formula R 38 CO C NXLIII 35 I NC/ R 38 CO directly attached by caibun atoms, where each R is an alkyl group of 1 to 4 carbon atoms, a chlorine atom, or a phenyl group, especially a methyl group.

1 n 14 1,7,63 Examples of photopolymerisable materials containing pyridinone units are those having, directly attached to carbon atoms, groups of the formula R 39 XLIV d XLIV N I where R 3 is an aliphatic or cycloaliphatic radical of 1 to 8 carbon atoms and 5 d has the meaning previously assigned.

Examples of compounds containing chalcone, propenone, or pentadienone groups are those containing structures of formula R 4 d O R 40 Rd d R R 41 or 10 R 40 \R 42-R 41 XLVI where each R"' is a halogen atom, or an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkoxy, cycloalkoxy, alkenoxy, cycloalkenoxy, carbalkoxy, carbocycloalkoxy, carbalkenoxy, or carbocycloalkenoxy group, such organic groups containing 1 to 9 carbon atoms, or is 15 a nitro group, or a carboxyl, sulphonic, or phosphoric acid group in the form of a salt, d and R 8 each having the meanings previously assigned, R 41 represents a valency bond or a hydrogen atom, R 2 represents a grouping of formula R 43 O R 44 20 I II XLVII -CH-=C C C=CH rnm n or 0 0 II II CH=C-CC-C CH 4 XLVIII R 45 1,575,653 is 1,575,653 or R 50 I 11 /R \o e 46 I -CHC-C II I L -C-C CH wherein R and R 4 are each individually a hydrogen atom, an alkyl group, e g, of 1 to 4 carbon atoms, or an aryl group of up to 12 carbon atoms, preferably a mono 5 nuclear group such as a phenyl group, or conjointly denote a polymethylene chain of 2 to 4 methylene groups, R 45 and R 46 are each a hydrogen atom, an alkyl group, e g, of 1 to 4 carbon atoms, or an aryl group of up to 12 carbon atoms, preferably a mononuclear group such as a phenyl group, and 10 m and N are each zero, 1, or 2, with the proviso that they are not both zero.

Suitable 3-substituted acrylates contain groups of the general formula R 7 CI-=C(R 27)COO L where R' is an aliphatic or mononuclear aromatic, araliphatic, or heterocyclyl group, 15 preferably of not more than 12 carbon atoms, having ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond shown, such as a phenyl, 2-furyl, 2 or 3-pyridyl, prop-2-enyl, or styryl group, and R 2 '7 has the meaning previously assigned.

Specific examples of such 3-substituted acrylates or disorbates and bis( 2-furyl 20 acrylates) of poly(oxyethylene) glycols and poly(oxypropylene)glycols.

If desired, a mixture of photopolymerisable compounds my be used Especially preferred photopolymerisable compounds are the disorbates and bis( 2furylacrylates) just mentioned.

The molar ratio of polyamide resin to photopolymerisable compound is such that 25 there is sufficient of each present to form both a satisfactory heatcurable composite and a satisfactory heat-cured composite Usually the molar ratio is from 10:1 to 1:10, and especially from 5:1 to 1:5.

Preferably the photopolymerisable compound is irradiated in the presence of a photopolymerisable catalyst Suitable catalysts are well known and are described in, 30 for example, the book by Kosar cited above.

Like the photopolymerisable compounds, the catalysts fall into two main classes(i) those which, on irradiation, give an excited state that leads to formation of free radicals which then initiate polymerisation of the monomer (photoinitiators) and (ii) those which, on irradiation, give an excited state that in turn transfers its 35 excitation energy to a molecule of the monomer, giving rise to an excited molecule of the monomer which then crosslinks with an unexcited molecule of hte monomer (photosensitisers).

The first class includes organic peroxides and hydroperoxides, a-halogen substituted acetophenones such as trichloromethyl 4 '-tert butyl phenyl ketone, benzoin 40 and its alkyl ethers, e g, the n-butyl ether, a-methylbenzoin, benzophenones, Oalkoxycarbonyl derivatives of an oxime of benzil or of 1 phenylpropane 1, 2 dione, such as benzil (O ethoxycarbonyl) a monoxime and 1 phenylpropane 1,2dione 2 (O ethoxycarbonyl)oxime, benzil acetals, e g, its dimethyl acetal, substituted thioxanthones, e g, 2 chloroethioxanthone, anthraquinones, and mixtures of 45 phenothiazine dyes (e g methylene blue) or quinoxalines (e g, metal salts of 2 (mor p methoxyphenyl) quinoxaline 6 ' or 7 ' sulphonic acids) with electron donors such as benzenesulphinic acid, toluenesulphinic acid, or other sulphinic acid or a salt thereof such as the sodium salt, an arsine, a phosphine, or thiourea (photoredox systems), these initiators being used with unsaturated esters, especially acrylates 50 and methacrylates, and also acrylamides.

The second class includes 5 nitroacenaphthene, 4 nitroaniline, 2,4,7 trinitro9 fluorenone, 3 methyl 1,3 diaza 1,9 benzanthrone, and bis(dialkylamino)benzophenones, especially Michler's ketone, ie, bis(p dimethylamino) benzophenone.

Suitable photopolymerisation catalysts are readily found by routine experimenta 55 W 16 1,575,653 1 tion The catalysts must not, of course, give rise to a substantial degree of photoinduced polymerisation of the polyimide resin, neither should any other substance present: further they must not cause curing of the polyamide resin under the conditions of photopolymerisation such that the resin does not remain substantially thermosettable 5 Generally, 0 1 to 20 %, and preferably 0 5 to 10 %, by weight of the photopolymerisation catalyst is incorporated, based on the weight of the photopolymerisable compound.

In the photopolymerising step actinic radiation of wavelength 200-600 nm is preferably used Suitable sources of actinic radiation include carbon arcs, mercury 10 vapour arcs, fluorescent lamps with phosphors emitting ultraviolet light, argon and xenon glow lamps, tungsten lamps, and photographic flood lamps Of these, mercury vapour arcs, particularly sun lamps, fluorescent sun lamps, and metal halide lamps are most suitable The time required for the exposure of the photopolymerisable compound will depend upon a variety of factors which include, for example, the individual 15 compound used, the amount of that compound on the reinforcement, the type of light source, and its distance from the impregnated material Suitable times may be readily determined by those familiar with photopolymerisation techniques, but in all cases the product after photopolymerisation must still be curable by heating: for this reason, photopolymerisation is carried out at temperatures below those where curing of the 20 polyimide resin by the heat-activated curing agent becomes substantial.

The temperatures and duration of heating required for the thermal curing and the proportions of curing agent are readily found by routine experimentation and easily derivable from what is already well known concerning the heatcuring of polyimide resins.

The polyimide resin, the photopolymerisable compound, the thermallyactivated curing agent, and, if used, the catalyst for the photopolymerisation, are preferably applied so that the heat-curable composite contains a total of from 20 to 80 % by weight of the said components, and, correspondingly, 80 to 20 % by weight of the reinforcement More preferably, a total of 30 to 50 % by weight of these components 30 and 70 to 50 % by weight of the reinforcement are employed.

As already indicated, when the polyamide resin and the photopolymerisable compound are applied as a film to a fibrous material in the production of prepregs, the components are caused to flow about the fibrous material by applying heat and/or pressure Of course, heating must not be to an extent such that the prepreg becomes 35 substantially heat-cured Heated platens or pairs of rollers may be used, for example, and in the latter case, when unidirectional fibres are used, a rolling pressure may be applied in the direction of the fibre alignment In place of pairs of rollers, the assembly may be passed under tension around part of the periphery of a single roller.

The film may be provided with a strippable backing sheet, e g, of a polyolefin 40 or a polyester, or of cellulosic paper having a coating of a silicone release agent, on the face opposite to that brought into contact with the fibrous reinforcement Manipulation of the assembly is often easier if the film has a tacky surface This may be produced by coating the film with a substance which is tacky at room temperature but which cures to a hard, insoluble, infusible resin under the conditions of heat 45 employed to cure the polyimide resin component of the film However, an adequate degree of tackiness often exists without additional treatment, especially, if the polyimide resin is not too advanced.

Prepregs may be made by a batch process, the fibrous reinforcing material being laid on the film of the photopolymerised composition, which is advantageously under 50 slight tension, when a second such film may, if desired, be laid on top and then the assembly is pressed while being heated.

Prepregs may also be made continuoously, such as by contacting the fibrous reinforcing material with the film of the photopolymerised composition, then, if desired, placing a second such film on the reverse face of the fibrous reinforcing 55 material and applying heat and pressure.

More conveniently, two such films, preferably supported on the reverse side by belts or strippable sheets, are applied simultaneously to the fibrous reinforcing material so as to contact each exposed face When two such films are applied, they may be the same or different 60 Multilayer prepregs may be made by heating under pressure interleaved films and layers of one or more fibrous reinforcing materials.

When unidirectional fibres are used as the reinforcement material, successive layers of them may be oriented to form cross-ply prepregs.

1.575,653 17 1575,653 17 1 With the fibrous reinforcing material there may be used additional types of reinforcement such as a foil of a metal (e g aluminium, steel, or titanium) or a sheet of a plastics material (e g, an aromatic or aliphatic polyamide, a polvimide, a polysulphone, or a polycarbonate) or of a rubber (e g, a neoprene or acrylonitrile rubber).

In the production of sheet moulding compositions, a mixture of the polyimide 5 resin, the photopolymerisable compound, the thermally-activated curing agent for the polyimide resin, and, if used, the catalyst for photopolymerisation, together with the chopped strand reinforcing material and any other components, are exposed to irradiation in layers through supporting sheets.

The composites may be heat-cured using conditions conventional for the heat 10 curing of polvimide resins.

The following Examples illustrate the invention Temperatures are in degrees Celsius and, unless otherwise indicated, parts are by weight Epoxide contents were determined by titration against a O 1 N solution of perchloric acid in glacial acetic acid in the presence of excess of tetraethylammonium bromide, crystal violet being 15 used as the indicator Flexural strengths are the mean of three results and were determined according to British Standard 2782, Method 304 B. Materials used in the Examples were prepared as follows:

Sorbate A To a stirred solution of 100 g of polyoxyethylene glycol (having an average 20 molecular weight of 200), 110 g of triethvlamine, and 500 ml of toluene at room temperature was added 130 5 g of sorbovl chloride over 30 minutes The mixture was then stirred at 80 C for 1 hour, cooled, and filtered Removal of the solvent under reduced pressure gave the desired polyoxvethylene disorbate.

Acrylate A 25 This is substantially 3-phenoxy-2-hydroxypropyl acrylate, and was obtained by adding, over 1 hour, 222 g of acrylic acid to 500 g of phenyl glycidyl ether (epoxide content 6 16 equiv /kg) stirred at 100 in the presence of 1 5 g of tetramethylammonium chloride and lg of 2,6-di-tert butyl-p-cresol, and stirring for a further 4 hours at 1000, at which time the epoxide content of the mixture had dropped to 0 92 30 equiv /kg.

EXAMPLE 1.

A mixture of 6 15 parts of 2,2 bis( 3 allyl 4 hydroxyphenyl)propane, 7 15 parts of bis( 4 maleimidophenyl)methane, 13 3 parts of Sorbate A, and 0 25 part of Michler's ketone was milled on a triple roll mill 35 A woven cloth of poly(p phenylene terephthalamide) fibres was impregnated with the above composition and irradiated on both sides by high pressure metal halide quartz arc lamps for 1 minute to give a prepreg A laminate was prepared from this prepreg by pressing four 15 cm-square pieces at 180 for 1 hour at a pressure of 1 4 MN/m 2 n 40 EXAMPLE 2.

A commercially available prepolymer of bis( 4 maleimidophenyl)methane and bis( 4 aminophenyl)methane ( 10 parts) was milled on a triple mill with 10 parts of Sorbate A containing 0 2 part of Michler's ketone.

Glass cloth was impregnated with this flowable composition and irradiated on 45 both sides by high pressure metal halide quartz arc lamps for 30 seconds to give a prepreg A laminate was prepared by pressing six 15 cm-square pieces at 180 for 1 hour at a pressure of 1 4 MN/im 2 The latter, which consisted of 40 2 / resin and 59.8 /o glass, had a flexural strength of 256 Mn/n'm 2.

EXAMPLE 3

A further sample ( 10 parts) of the prepolymer used in Example 2 was dissolved, 50 together with 2 parts of benzil dimethyl acetal, in 10 parts of Acrylate A.

Glasscloth impregnated with this composition was irradiated for 5 minutes on both sides with high pressure metal halide quartz lamps A four-ply laminate was made by pressing 15 cm square pieces of the prepreg at 170 for 1 hour at a pressure of 55 1.4 MN/im 2.

1.575,653 EXAMPLE 4.

A composition, as described in Example 2 but containing 0 4 part of Michler's ketone, was applied to silicone-coated paper as a layer 36 Elm thick and then irradiated for 2 minutes with a high pressure metal halide-quartz arc lamp to form a film A carbon fibre prepreg was made by placing such a film on both faces of unidirectional carbon fibres ( 1 8 tows per cm, each tow weighing 0 2 g/m) and pressing for 5 minutes at 100 under an applied pressure of 0 07 MN/m 2.

A six-ply laminate was made by pressing 10 cm-square pieces of the prepreg for for 1 hour under a pressure of 1 4 MN/m 2 The laminate, which consisted of 64 5 % of carbon fibre, had a flexural strength of 226 Mn/m 2.

Claims (1)

1. WHAT WE CLAIM IS:-

   1 Thermosettable composites comprising:(a) a fibrous reinforcing material, (b) a heat-curable polyimide resin containing, two groups of formula per average molecule, at least I directly attached to carbon atoms, where D denotes // CI-I-C, CH 2 =C, or CH CH 2 / CH CH (c) a heat-activated curing agent for the said resin, and (d) a photopolymerised compound.

   2 Composites according to claim 1, in which the resin (b) is of the formula II a where D has the meaning assigned in claim 1, R' is an organic group of valency (a+ 1), containing from 2 to 30 carbon atoms, and ais 1 or 2.

   3 Composites according to claim 2, where R' in the formula denotes a linear or branched alkylene radical of 2 to 12 carbon atoms; a phenylene radical, optionally substituted in the ring by 1 to 3 methyl groups; a cyclohexylene radical, optionally substituted in the ring by 1 to 3 methyl groups; a radical of formula ?-( CH 2, (C b__ 1,575,653 1,575,653 or R 2 R 3-1 C-C= O 1 1 iv -C 3 H 6-N or R 2 j F? 3 R 4 'CR 5-C c O 1 1-CA31 #5 & V 1 v c 11 -R 61 P R _a c v or V 1 or vil or R 9 d viii /N-C 3 H 6M% 11 CH 2 H 2 d Ri I i 7565 K 20or R 9 di9 I d R 10 RX where a has the meaning assigned in claim 2, b is an integer of from 1 to 3, 5 c denotes zero or 1, d denotes zero or an integer of 1 to 4, R 2, R 3, R', and R' each denote a hydrogen atom or the same or a different aliphatic hydrocarbon group of 1 to 6 carbon atoms, with the proviso that R 2 and R 3 may alternatively, together with the carbon atom to which they are attached, form a 10 or 6-membered aliphatic ring; R 6 denotes an aromatic residue of valency a+ 2, containing 6 to 15 carbon atoms, R' denotes a monovalent aromatic group of 6 to 15 carbon atoms, Rs denotes an oxygen or sulphur atom, R 9 denotes a methyl group or a chlorine atom, and 15 R' denotes a carbon-carbon bond, or an atom or group of formula O, -S-, -CO-, -CH 2-, -C(CHI:) 2-, -SO 02-, CONH-, -COO-, -CONHR CONH-, -N:N-, or -NR'-, where R 1 has the meaning assigned in claim 2 or 3.

   4 Composites according to claim 3, in which, in formula VI, R 6 denotes a mono 20 nuclear benzenoid group or a dinuclear group the nuclei of which may be joined through an oxygen atom, an alkylene group, or a sulphonyl group.

   Composites according to claim 3 or 4, in which, in formula VI, R' denotes a mononuclear benzenoid group.

   6 Composites according to claim 2, where R' denotes a phenylene radical sub 25 stituted in the ring by 1 to 3 fluorine, chlorine, or bromine atoms.

   7 Composites according to claim 3, where R, denotes a dinuclear benzenoid group, the nuclei of which are fused or joined by a carbon-carbon bond only.

   8 Composites according to claim 1, wherein the resin (b) is bis( 4 maleimidophenyl)methane, bis( 4 itaconamidophenlyl)methane, bis( 4 citraconamidophenyl) 30 methane, 2,2 bis( 4 maleimidophenyl)propane, bis( 4 maleimidophenyl) sulphone, bis( 4 maleimidophenyl) ether, bis( 4 maleimidophenyl) ketone, 1,6 bis(maleimido)hexane, or a compound of formula 7 I 7 l CO Co CO CO CH 2 CH 2 x CO CO 9 Composites acording to claim 1, wherein the said (b) is 1,3 or 1,4 35 di (maleimido) benzene.

   Composites according to any preceding claim, wherein the heat-curing agent (c) is a diamine or triamine of formula 1.575653 11 5 2 H 2 N-Rl-f-NH 2 l XI where R' has the meanings assigned in any of claims 2 to i and a has the meaning assigned in claim 2.

   11 Composites according to any of claims 1 to 9, wherein the heat-curing agent 5 is a diamine or triamine of formula HN-R- NH 2 l XI where R 1 has the meaning assigned in claim 6 and a has the meaning assigned in claim 2 10 12 Composites according to any of claims 1 to 9, wherein the heat-curing agent (c) is bis( 4 aminophenyl)methane, bis( 4 aminophenyl) phenyl phosphate, mphenylenediamine, hexamethvlenediamine, 1,3 bis(aminopropyl) 5,5 dimethylhydantoin, or 2,2 bis( 4 aminophenyl)propane.

   13 Composites according to any of claims 1 to 9, wherein the heat-curing agent S 15 (c) is a polyhydric phenol.

   14 Composites according to claim 13, wherein the polyhydric phenol is hydroquinone, phloroglucinol, pyrocatechol, resorcinol, or of formula R 11 R 1 " HO OH HO,,bc R 123 g O XII where 20 R' is chlorine or bromine, R 12 denotes -CH,-2-, -C(CH 3)2-, -SO 2-, or -S-, and c and d have the meanings assigned in claim 3, 1,4 dihvdroxynaphthalene, a phenol formaldehyde novolak, a cresol formaldehyde novolak, a p chlorophenol formaldehyde novolak, a p tert butylphenol 25 formaldehyde novolak, a p octylphenol formaldehyde novolak or a p nonylphenolformaldehyde novolak.

   Composites according to any of claims 1 to 9, in which the heat-curing agent (c) is an alkenylphenol or an ether thereof.

   16 Composites according to claim 15, in which the heat-curing agent is an ether 30 of an alkenylphenol with a saturated or ethylenically unsaturated aliphatic alcohol containing up to 6 carbon atoms.

   17 Composites according to claim 15 or 16, in which the heat-curing agent is an allyl or methallyl-substituted phenol or an ether thereof.

   18 Composites according to claim 17, in which the heat-curing agent is eugenol, 35 its methyl ether, or a compound of formula CH 2 CH-CH 2 1 2 HO/\/ OH XIII CH 2-CHCH 2 where R 12 has the meaning assigned in claim 14 and c has the meaning assigned in claim 3 4 ( 1.575 653 19 Composites according to any of claims 1 to 9, in which the heat-curing agent (c) is a polvhydric alcohol.

   Composites according to claim 19, in which the polvhydric alcohol is a branched or straight chain aliphatic alcohol of 2 to 12 carbon atoms, or a cycloaliphatic or cvcloaliphatic-aliphatic alcohol of tun to 12 carbon atoms with one or more cyclo 5 aliphatic nuclei, which may be joined by an oxygen or sulphur atom, a carbon-carbon bond, or an aliphatic group, wherein the hydroxyl groups are attached to either aliphatic or cycloaliphatic residues.

   21 Composites according to claim 19, in which the polyhydric alcohol is of formula 10 R 12 3 xiv or R 13 R 13 I I HOCHCH 20 L 2 O CH 2 CHOH R 12 C < xv or R 13 R 13 I 15 HOCHCH 20 R 120 OCH 2 CHOH R 12C XVI where R 2 has the meaning assigned in claim 14, c has the meaning assigned in claim 3, and each RW 3 denotes a hydrogen atom or a methyl group.

   22 Composites according to any of claims 1 to 9, in which the heat-curing agent 20 (c) is a polvcarboxylic acid.

   23 Composites according to claim 22, in which the heat-curing agent is an aliphatic dicarboxylic acid of 4 to 10 carbon atoms.

   24 Composites according to any of claims 1 to 9, in which the heat-curing agent (c) is an azomethine of formula 25 R 15 R-4 C =C=N-R 16 XVII or R 154 c=NR 6 R 15 XVIII Rl-=NR N ' XVIII 1,575,653 or R 14 R 14 R l R'4-N =C-R 17-C=N-R 6 le in which RW 4 denotes a hydrogen atom, a linear or branched aliphatic radical of up to 12 carbon atoms, a cycloaliphatic or cycloaliphatic-aliphatic radical of up to 12 carbon 5 atoms, an aromatic radical of 6 to 12 carbon atoms, an araliphatic radical of 7 to 20 carbon atoms, a heterocyclic radical of 4 to 7 carbon atoms, or a heterocyclic-aliphatic radical of 5 to 18 carbon atoms, R' and R" 6 has the same meaning as R'4 except that they cannot denote a hydrogen atom, with the proviso that R'4 and Rs in formulae XVII and XVII 1, 10 together with the carbon atom to whichi they are attached, can also denote a 5 or 6membered aliphatic ring, RW 7 denotes a divalent linear or branched aliphatic radical with up to 12 carbon atoms, a divalent cycloaliphatic or cycloaliphatic-aliphatic radical with up to 12 carbon atoms, a divalent aromatic radical of 6 to 12 carbon atoms, a divalent araliphatic 15 radical of 7 to 18 carbon atoms, a divalent heterocyclic radical of 4 to 7 carbon atoms, or a divalent heterocyclic-aliphatic radical, and R' is a divalent radical having the meaning assigned in any of claims 2 to 6.

   Composites according to any of claims 1 to 9, in which the heat-curing agent (c) is an azomethine of formula 20 R's R 14-C = N -R 16 XVII or R's R 16 l l XVIII Rx 4 _C =N-R-_N= C-R 14 XVIII or R 14 R 14 25 R' 4 -N=C-R 174 =N _R XIX 25 in which R 4 denotes a hydrogen atom, a linear or branched aliphatic radical of up to 12 carbon atoms, a cycloaliphatic or cycloaliphatic-aliphatic radical of up to 12 carbon atoms, an aromatic radical of 6 to 12 carbon atoms, an araliphatic radical of 7 to 20 carbon atoms, a heterocyclic radical of 4 to 7 carbon atoms, or a heterocyclic-aliphatic 30 radical of 5 to 18 carbon atoms.

   R and R 16 have the same meaning as RW 4 except that they cannot denote a hydrogen atom, with the proviso that RW 4 and R'5 in formulae XVII and XVIII, together with the carbon atom to which they are attached, can also denote a 5 or 6-membered aliphatic ring, 35 R 7 denotes a divalent linear or branched aliphatic radical with up to 12 carbon atoms, a divalent cycloaliphatic or cvcloaliphatic-aliphatic radical with up to 12 carbon atoms, a divalent aromatic radical of 6 to 12 carbon atoms, a divalent araliphatic radical of 7 to 18 carbon atoms, a divalent heterocyclic radical of 4 to 7 carbon atoms, or a divalent heterocyclic-araliphtic radical, and 40 R' is a divalent radical having the meaning assigned in claim 3 or 6.

   26 Composites according to any of claims 1 to 9, in which the heat-curing agent (c) is a dimeric, or oligomeric, halogen-containing bis(cyclopentadienyl) compound of formula 1,575,653 24 1,575,653 (H)4-e R 13 R 13 XX -CH 2 CH 2 xx (R 18)e where RWS denotes a fluorine, chlorine, or bromine atom, e is an integer of 1 to 4, each R 3 has the meaning assigned in claim 21, and 5 f is an integer of average value 2 to 20.

   27 Composites according to any of claims 1 to 9, in which the heat-curing agent (c) is fi-aminocrotonic acid or a derivative thereof.

   28 Composites according to claim 27, in which the heat-curing agent is of one of the formulae 10 NHR 19 CH 3 C-CHCOO R 20 XXI _ -9 _g NHR 19 XXII CH 3 C=CHCONR 19 _-g NHR 19 R 21 NHR 19 CH 3 C-CHCON R 2 INCOCH-CCH 3 \R 213 1 XXIII CH 3 R 190 COCH= CNH R 20 XXIV g _-9 R 22 CH 3 I I 1 1 1 3 xxv R 19 NCOCH=C-NR 19-R 20 15 A 1 575 653 NHR 19 CH 3 C-=CHCOR 23 R 24 xx VI and NHR 19 R 19 NHR 19 {, 20 1 1 M CH 3 C-CHCOOR 20 NCOCH==CCH 3 where RR and R 22 each denote a hydrogen atom or a linear, branched, or cyclic hydro 5 carbon radical of 1 to 9 carbon atoms, R 2 denotes a divalent linear, branched, or cyclic hydrocarbon radical with 2 to carbon atoms, or a heterocyclic ring containing one or more nitrogen, oxygen, or sulphur atoms, R 2 and R 2, are such as to form with the two indicated nitrogen atoms a hetero 10 cyclic five or six-membered ring, R 23 denotes -0 or -NH-, R 2 " denotes a linear, branched, carbocyclic or heterocyclic radical with 3 to 6 carbon atoms, having a group suitable for polymerisation, and g is an integer of 2 to 4 15 29 Composites according to any of claims 1 to 9, in which the heat-curing agent (c) is indole or a derivative thereof.

   Composites according to claim 29, in which the heat-curing agent is of the formula N R 26 XXIX 20 R 25 where R 2 denotes a hydrogen atom, an alkyl group of 1 to 4 carbon atoms, or an acyl group of 2 to 5 carbon atoms, and R 2 denotes a hydrogen atom or an alkyl group of 1 to 4 carbon atoms.

   31 Composites according to any of claims 1 to 9, in which the heat-curing agent 25 (c) is 2,2,4-trimethyl-1,2-dihydroquinoline.

   32 Composites according to claim 1, in which the resin (b) is as specified ii any of claims 1 to 5, 7, and 8 and the heat-curing agent (c) is as specified in any of claims 1, 10, 12 to 24, and 26 to 30.

   33 Composites according to any of claims 6 and 9 to 31, in which the resin (b) 30 is present as a prepolymer with the heat-curing agent (c).

   34 Composites according to any of claims 1 to 5, 7, 8, and 32, in which the resin (b) is present as a prepolymer with the heat-curing agent (c).

   Composites according to any preceding claim, in which the photopolymerised compound (d) has been photopolymerised through a free-radical chain reaction 35 36 Composites according to claim 35, in which component (d) has been obtained by photopolymerisation of a photopolymerisable compound containing one ethylenic linkage or, providing they are unconjugated, more than one.

   37 Composites according to claim 36, in which said photopolymerisable compound is an acrylic ester containing at least one group of formula 40 CH = C(R 2)COO XXX or r lCH 2 = C(R 2)CONH-±CHCOO XXXI or CH 2 = C(R 2)CONHCH(OH) CH 2 COO XXXII where R 2 is a hydrogen, chlorine, or bromine atom or an alkyl hydrocarbon group of 1 to 4 carbon atoms.

   38 Composites according to claim 37, in which the acrylic ester is one of the formulae CH 2 CHCOO-(CH 2-CHR 28/c CHO-OCCH-CH 2 R 29 J XXXII or R 30 CH 2 =CHCOO -(CH 2)k C - R 31 10 R 28 je XXXIV or CH 2 =CHCOO-CH 2 CHCH 20-(CO Jc R 32 OH _e XXXVI or R C±CH 2 OOCCH = CH 2 l XXXVII or 15 CH 2 = CHCOOR" 4 XXXVIII where c has the meaning assigned in claim 3, e has the meaning assigned in claim 26, h is an integer of from 1 to 8, 20 j is an integer of from 1 to 20, k is zero or a positive integer, provided that c and k are not both zero, R 29 denotes -H, -OH, or -OOCCH=CH 2, R 29 denotes -H, -CH:,, CH,, -CH 2 OH, or -CH 200 OCCH=CH 2, R 30 denotes -H, -Cl, CH,, or -C 2 H 5, 25 R 3 ' denotes an organic radical of valency e, linked through a carbon atom or carbon atoms thereof to the indicated e terminal oxygen atoms, R'2 denotes an organic radical of valency e, linked through a carbon atom thereof other than the carbon atom of a carbonyl group, R 3 denotes CH,-, C 2 H 5-, or CH 2 =CHCOOCH, and 30 R 4 denotes either an alkyl group of 1 to 6 carbon atoms, optionally substituted bv one hydroxyl group, or a dialkylaminoalkyl group containing in all 3 to 12 carbon atoms.

   1.575 653 .1 7 -v 5 2 39 Composites according to claim 37, in which the acrylic ester is 2,2dimethylpropane-1,3-diol diacrylate.

   Composites according to any of claims 1 to 33, in which the photopolymerised compound (d) is provided by a photopolymerisable compound which has been photopolymerised by reaction of an excited molecule of the monomer with an unexcited 5 molecule of the monomer.

   41 Composites according to claim 40, in which the photopolymerisable compound has at least two groups which are azido, coumarin, stilbene, disubstituted maleimide, pyridinone, chalcone, propenone, or pentadienone groups, or at least two acrylic acid groups which are substituted in their 3-position by groups having ethylenic un 10 saturation or aromaticity in conjugation with the ethylenic double bond of the acrylic group.

   42 Composites according to claim 41, in which the photopolymerisable compound contains at least two groups of the formula N 3-R 35 XXXIX 15 or N 3-SO 2 R 83-_ XL where R denotes a mononuclear or dinuclear aromatic radical containing from 6 to 12 carbon atoms.

   43 Composites according to claim 41, in which the photopolymerisable compound 20 contains at least two groups of the formula O=C I R 36 XLI I L where R" 6 is an oxygen atom, a carbonyloxy group, a sulphonyl group, or a sulphonyloxy group.

   44 Composites according to claim 41, in which the photopolymerisable compound 25 contains at least two groups of the formula P 37 XLII where R 7 is the residue, containing up to 8 carbon atoms in all, of a five or sixmembered nitrogen-containing heterocyclic ring, fused to a benzene or naphthalene nucleus, and linked through a carbon atom of the said heterocyclic ring adjacent to a 30 nitrogen hetero atom thereof to the indicated benzene nucleus.

   Composites according to claim 41, in which the photopolymerisable compound contains at least two groups of the formula R 38 CO \C/ \ II N XLIII -CN R 38 ' Co directly attached to carbon atoms, where each R is an alkyl group of 1 to 4 carbon 35 atoms, a chlorine atom, or a phenyl group.

   l 57 i 653 28 1 575; 653 46 Composites according to claim 41, in which the photopolymerisable compound contains, directly attached to carbon atoms, at least two groups of the formula R 39 d L N XLIV where R 39 is an aliphatic or cycloaliphatic radical of 1 to 8 carbon atoms and 5 d has the meaning assigned in claim 3.

   47 Composites according to claim 41, in which the photopolymerisable compound contains at least two groups of the formula R 4 0 R d d XLV 4 R or 10 R 40 | vi \ R 42 AJ_ 7 j-4 R 41 XLVI where each R 40 is a halogen atom, or an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkoxy, cycloalkoxy, alkenoxy, cycloalkenoxy, carbalkoxy, carbocycloalkoxy, carbalkenoxy, or carbocycloalkenoxy group, such organic groups containing 1 to 9 carbon atoms, or is a 15 nitro group, or a carboxyl, sulphonic, or phosphoric acid group in the form of a salt, d has the meaning assigned in claim 3, R" represents a valency bond or a hydrogen atom, R 42 represents a grouping of formula R 43 O R 44 XLVII 20 I __ _ _ _ _ _ _ _ _ II __ _ _ _ _ _ _ I_ _ _ _ _ _ _ CH-CC CC-=CH I'Dm n or 0 0 11 C-C=CHH R i R -Z R 46 XLVIII R 45 or 2 Q I A 7 65 I I 9 R 450 o RO I II / \ R 46 I -CH= C<;"-l CH C-C=CHwherein R 43 and R 44 are each individually a hydrogen atom, an alkyl group, or an aryl group of up to 12 carbon atoms, or R' and R 44 conjointly denote a polymethylene chain of 2 to 4 methylene groups, 5 R 45 and R 46 are each a hydrogen atom, an alkyl group, or an aryl group of up to 12 carbon atoms, m and N are each zero, 1, or 2, with the proviso that they are not both zero, and R' has the meaning assigned in claim 3.

   48 Composites according to claim 41, in which the photopolymerisable compound 10 contains at least two groups of the formula R 47 CH = C(R 2 ') COO where R'" is an aliphatic or mononuclear aromatic, araliphatic, or heterocyclyl group which has ethylenic unsaturation or aromaticity in conjugation with the ethylenic 15 double bond shown and R 2 '7 has the meaning assigned in claim 37.

   49 Composites according to claim 48, in which the photopolymerisable compound is a disorbate or a bis( 2-furylacrylate) of a poly(oxyethylene) or a poly(oxypropylene) glycol 20 Composites according to claim 1 or 34, in which the heat-curable resin (b) is as specified in any of claims 1 to 5 and 8, the heat-activated curing agent (c) is as specified in any of claims 10, 12 to 24, and 26 to 30, and the photopolymerised compound (d) is specified in claim 35 or 40 or one obtained by photopolymerisation of a photopolymerisable substance as specified in any of claims 36 to 38 and 41 to 49 25 51 Composites according to any of claims 6, 7, 9 to 31, and 35 to 49, in which the molar ratio of the heat-curable resin (b) to the compound photopolymerised to form component (d) is from 10:1 to 1:10.

   52 Composites according to any of claims 1 to 5, 8, 32, 34, and 50, in which the molar ratio of the heat-curable resin (b) to the compound photopolymerised to form 30 component (d) is from 10:1 to 1:10.

   53 Composites according to claim 1, substantially as described herein.

   54 Composites according to claim 1, substantially as described in any of Examples l to 3.

   55 Composites according to claim 1, substantially as described in Example 4 35 56 A method of preparing a composite according to any of claims 6, 7, 9 to 31, 33, 35 to 49, 51, 53, and 55, which comprises i) impregnating a fibrous reinforcing material with a liquid composition comprising (b) a heat-curable polyimide resin, 40 (c) a heat-activated curing agent for a polyamide resin, (d) a photopolymerisable compound (other than a heat-curable polyimide resin) and, if desired, (e) a photopolymerisation catalyst for the compound (d), and ii) in the absence of a substance which gives rise to a substantial degree of 45 photoinduced polymerisation of the polyimide resin, exposing the impregnated material to actinic radiation such that the composition solidifies due to photopolymerisation of the photopolymerisable compound while the polyimide resin remains substantially in the thermosettable state.

   57 A method of preparing a composite according to any of claims 1 to 5, 8, 32, 50 34, 50, 52, and 54, which comprises i) impregnating a fibrous reinforcing material with a liquid composition comprising (b) a heat-curable polyimide resin, (p) a heat-activated curing agent for a polyimide resin, 55 1.575 653 (d) a photopolymerisable compound (other than a heat-curable polyimide resin) and, if desired, (e) a photopolymerisation catalyst for the compound (d), and ii) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of the polyimide resin, exposing the impregnated material 5 to actinic radiation such that the composition solidifies due to photopolymerisation of the photopolymerisable compound while the polyimide resin remains substantially in the thermsettable state.

   58 A method according to claim 56 or 57, substantially as described herein.

   59 A method according to claim 57, substantially as described in any of Examples 10 1 to 3.

   A method of preparing a composite according to any of claims 6, 7, 9 to 31, 33, 35 to 49, 51, 53, and 55, which comprises i) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of a polyimide resin, exposing to actinic radiation a layer of 15 a liquid composition comprising (b) a heat-curable polyimide resin, (c) a heat-activated curing agent for a polyimide resin, (d) a photopolymerisable compound (other than a heat-curable polyimide resin), and, if desired, 20 (e) a photopolymerisation catalyst for the compound (d), until the said composition solidifies to form an essentially solid film due to photopolymerisation of the said photopolymerisable compound while the polyimide resin remains substantially in the thermosettable state, and, ii) bringing together the film so formed and fibrous reinforcing material under 25 conditions such that the said film flows about the fibres and the components of the said film and the fibres form a coherent structure but the polyimide resin remains substantially thermosettable.

   61 A method of preparing a composite according to any of claims 1 to 5, 8, 32, 34, 50, 52, and 54, which comprises 30 i) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of a polyimide resin, exposing to actinic radiation a layer of a liquid composition comprising (b) a heat-curable polyimide resin, (c) a heat-activated curing agent for a polyimide resin, 35 (d) a photopolymerisable compound (other than a heat-curable polyimide resin), and, if desired, (e) a photopolymerisation catalyst for the compound (d), until the said composition solidifies to form an essentially solid film due to photopolymerisation of the said photopolymerisable compound while the polyimide 40 resin remains substantially in the thermosettable state, and ii) bringing together the film so formed and fibrous reinforcing material under conditions such that the said film flows about the fibres and the components of the said film and the fibres form a coherent structure but the polyimide resin remains substantially thermosettable 45 62 A method according to claim 60 or 61, substantially as described herein.

   63 A method according to claim 60, substantially as described in Example 4.

   64 Composites made by the method of any of claims 56, 58, 60, 62, and 63.

   Composites made by the method of any of claims 57, 59, and 61.

   66 A method of making a reinforced composite which comprises heat-curing a so 50 composite as claimed in any of claims 1 to 5, 8, 32, 34, 50, 52, 54, and 65.

   67 A method of making a reinforced composite which comprises heat-curing a composite as claimed in any of claims 6, 7, 9 to 31, 33, 35 to 49, 51, 53, 55, and 64.

   68 Heat-cured, reinforced composites made by the method of claim 66.

   69 Heat-cured, reinforced composites made by the method of claim 67.

   T SHARMAN.

   Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1980.

   Published by the Patent Office, 25 Southampton Buildings, London, WVC 2 A l AY, from which copies may be obtained.

   1.5755 a 65